System and method for connecting electrical devices using fiber optic serial communication

ABSTRACT

A system and method for communicating between serially connected electrical devices of a network is provided. The network includes a series of electrical devices, and fiber optic connectors between electrical devices of the series of electrical devices forming a closed communication ring in which output of each electrical device is communicatively connected to input of a subsequent electrical device of the series of electrical devices.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 11/042,588, filed Jan. 24, 2005 now U.S. Pat. No.7,388,189 entitled “SYSTEM AND METHOD FOR CONNECTING ELECTRICAL DEVICESUSING FIBER OPTIC SERIAL COMMUINCATION”, which claims priority under 35U.S.C. §119 to U.S. Provisional Application Ser. No. 60/622,479, filedon Oct. 27, 2004, and entitled “Fiber Optic Daisy Chain for ElectricalDevices/Meters”, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to connecting electrical devices. In particular,this invention relates to a system and method for connecting electricaldevices using a fiber optic serial communication configuration.

2. Description of the Related Art

In a master/slave configuration, digital communication is providedbetween a master device and a plurality of slave devices so that themaster may communicate with individual slaves. One configuration is aserial communication (e.g., daisy chain) configuration in which an inputchannel or port of each device is connected to an output channel or portof an adjacent device, forming a closed ring, where one of the devicesis a master device and the rest of the devices are slave devices. In acommon configuration, the devices are connected using a network based onelectrically based serial communication standards, such as RS485hardware and software standards using a 4-wire or 2-wire communicationsystem, where the devices are connected by an electrically conductivecable (e.g., a copper cable). Bi-directional communication may beprovided over a pair of wires of the RS485 hardware. However, the RS485is limited in accordance with speed constraints inherent to propagationspeeds along electrically conductive cable (e.g., copper cable).Additionally, the electrically conductive cable is inherentlysusceptible to noise, poor grounding, power surges and attenuation ofpropagated signals towards the end of the chain, which may disruptcommunication and/or cause damage to one or more devices of the network.

One application for a master/slave configuration using a serialcommunication configuration is linking of slave meters, such as water,voltage, current and/or power meters, to a master unit. The master unitmay be, for example, a remote terminal unit (RTU) which may be locatedat a substation, such as a power plant supplying the power beingmeasured. The RTU may query the individual meters for retrieving datafrom the respective meters. The RTU and/or meters may be located inenvironments in which electrical activity, including high voltage,current and/or power conditions, may generate electromagnetic fieldsand/or other conditions which typically cause detrimental noise alongelectrically conductive cable and/or may cause damage to respectivehardware.

A certain degree of protection has been provided to devices along such anetwork by providing optical-electrical isolation to individual devices.However, the connections between the devices are still electrical andprone to noise, electrical transients, arcing, etc., particularly whenin proximity to a high degree of electrical activity.

Propagation speed limitations may be overcome by using fiber-opticconnections between devices. Furthermore, fiber-optic cables are notelectrically conductive and are not susceptible to noise, poor groundingor power surge related problems. However, multiple data streams mayresult in catastrophic data collisions. A fiber-optic interface betweena device and a fiber optic cable requires a dedicated input channel anda dedicated output channel in order to provide bi-directionalcommunication.

Accordingly, it is an aspect of the present disclosure to provide asystem and method for configuring a network of master/slave devicesusing a serial communication configuration which overcomes thelimitations of a network using electrically conductive cables, and whichovercomes the limitations of fiber optical cables in prior art serialcommunication configurations.

SUMMARY OF THE INVENTION

In accordance with the present disclosure, circuitry for connecting adevice to a network having a series of electrical devices, such aselectrical meters, is provided. The circuitry includes an input channelfor receiving a light signal from an output channel of a precedingelectrical device of the series of electrical devices; light to voltageconverter (LVC) circuitry for receiving the light signal from the inputchannel and converting the light signal to a voltage signal andproviding the voltage signal to a processor of the electrical device;voltage to light converter circuitry (VLC) for receiving the convertedvoltage signal and the output results from the processor and convertingthe received signal to a light signal; and an output channel foroutputting the light signal from the VLC to a subsequent electricaldevice of the series of electrical devices.

In another embodiment of the disclosure, an electrical device isprovided. The electrical device includes an input channel for receivinga light signal; LVC circuitry for receiving the light signal from theinput channel and converting the light signal to a voltage signal; aprocessor for receiving the voltage signal, processing the voltagesignal and outputting results of the processing; VLC circuitry forreceiving the converted voltage signal and the output results from theprocessor and converting the received signal to a light signal; and anoutput channel for outputting the light signal from the VLC.

In still another embodiment of the disclosure, a network of seriallyconnected electrical devices is provided. The network includes a seriesof electrical devices and fiber optic connectors between electricaldevices of the series of electrical devices forming a closedcommunication ring in which output of respective electrical devices iscommunicatively connected to an input of a subsequent electrical deviceof the series of electrical devices.

In a further embodiment of the disclosure, an electrical device of aplurality of serially connected electrical devices is provided. Theplurality of serially connected electrical devices form a closedcommunication ring in which an output of a respective electrical deviceof the plurality of serially connected electrical devices iscommunicatively connected to an input of a subsequent electrical deviceof the plurality of serially connected electrical devices. Theelectrical device includes a processor for receiving, processing andoutputting signals; circuitry for receiving light signals from apreceding electrical device of the plurality of serially connectedelectrical devices, converting the received light signals intoelectrical signals and providing the electrical signals to theprocessor. The electrical device further includes circuitry forreceiving electrical signals output from the processor, convertingreceived electrical signals into light signals and providing the lightsignals to the subsequent electrical device of the plurality of seriallyconnected electrical devices, wherein the light signals are propagatedbetween electrical devices of the plurality of serially connectedelectrical devices primarily via fiber optic connectors.

In still another embodiment of the disclosure, a method is provided forcommunicating light signals between an electrical device and otherelectrical devices of a series of electrical devices. The methodincludes the steps of communicating with at least one electrical deviceof the series of electrical devices configured in a closed communicationring having a daisy chain configuration in which an output channel ofrespective electrical devices of the series of electrical devices iscommunicatively connected by a fiber optic connector to an input channelof a subsequent electrical device of the series of electrical devices;and receiving a light signal in an electrical device of the series ofelectrical devices from a preceding electrical device of the series ofelectrical devices; and processing the received light signal usingdigital processing circuitry.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be described herein below withreference to the figures wherein:

FIG. 1 is a schematic diagram of a network of master/slave electricaldevices in a serial communication configuration in accordance with thepresent disclosure; and

FIG. 2 is a block diagram of circuitry associated with slave devices ofthe network shown in FIG. 1;

FIG. 3 is a block diagram of circuitry associated with the master deviceof the network shown in FIG. 1; and

FIG. 4 is a schematic diagram of the network of electrical devices inaccordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With respect to FIG. 1, a network of electrical devices 10 is shown. Thenetwork 10 includes electrical devices 14 communicatively connected in aseries, where the series includes n devices 14 ₁-14 _(n). One of thedevices 14, shown as device 14 ₁, is a master device, while theremaining devices 14 ₂-14 _(n) are slave devices. The devices each havean input channel 16 and an output channel 18. The series of devices 14are connected in series in a closed loop for forming a closedcommunication ring, in which the output channel 18 of respective devices14 is communicatively connected to the input channel 16 of a subsequentdevice 14, in the series, which is preferably the next device 14 in theseries. The output channel 18 of device 14 _(n) is communicativelyconnected to the input channel 16 of the master device 14 ₁.

Devices (preferably adjacent devices) in the series are communicativelyconnected via fiber optic connectors 20 for transmitting light signalsbetween the connected devices 14.

The respective slave devices 14 ₂-14 _(n) have a processor 24 andassociated interface circuitry 26 for interfacing between the fiberoptic connector 20 and the processor 24. The master device 14 ₁ has aprocessor 28 and associated interface circuitry 30 for interfacingbetween the fiber optic connector 20 and the processor 28. The processor24 has an input/output (I/O) channel 32 which may be conceptuallydescribed as including an input channel 34 and an output channel 36. Theprocessor 28 has an input/output (I/O) channel 40 which may beconceptually described as including an input channel 42 and an outputchannel 44. A communication path 50 is provided between the I/O channel32 and the interface circuitry 26 and between the I/O channel 40 and theinterface circuitry 30. The communication path 50 for the respectivedevices 14 may be a communication path that is known in the art, such asan electronic conductor or a wireless connection.

The I/O 32 of processor 24 may include input and output channels 34 and36 for receiving incoming data and transmitting outgoing data,respectively. The input and output channels 34 and 36 may sharecomponents, where the I/O 32 recognizes the direction of the data flowand dedicated and/or shared components of the appropriate channel 32 or34 direct the data in the proper direction. Similarly for the I/O 40 ofprocessor 28, where the input and output channels 42 and 44 may sharecomponents, and I/O 40 recognizes the direction of the data flow anddedicated and/or shared components of the appropriate channel 42 or 44direct the data in the proper direction.

In the master/slave configuration shown, the master device 14 ₁ sends amaster message to a selected slave device 14 _(m) (for m within therange between 2 and n, inclusive). The master message has an associatedaddress identifying the slave device 14 _(m). Preferably, only the slavedevice 14 _(m) which has an assigned address that corresponds to theaddress associated with the master message processes and/or responds tothe non-address portion of the master message. Accordingly, theaddressed slave device 14 _(m) may send a reply message in response tothe master message. The master reply messages all propagate in onedirection about the communication ring. In order to avoid datacollisions, the master device 14 ₁ waits for an expected reply to arrivebefore sending a subsequent (or next) master message.

The slave and master devices 14 may include similar or identicalcomponents (e.g., processors and/or interfaces), or the components maybe different. However, the master and slave devices 14 operatedifferently and must be configured to operate differently. It iscontemplated that a device may be configured to operate in a first modeas a master device 14 ₁ or in a second mode as a slave device 14 _(m),such as by executing the appropriate software to operate as the masteror slave, and/or by bypassing circuitry that should not be active duringoperation, in accordance with the mode selected. Such bypassing may beperformed, for example, via hardwiring, selecting a switch position,software control, etc. The slave devices 14 may all be substantiallyidentical, with each slave device 14 _(m) having a preferably uniqueaddress assignment. It is further contemplated that the slave devices 14may be different from one another, where the differences may betransparent to the master device 14 ₁, or they may be known to themaster device 14 ₁ so that the master device may account for thedifferences by making adjustments to the master messages sent, theprotocol used and/or the processing of the reply messages. It is typicalfor the slave devices 14 _(m) to have relatively simple processingcapabilities relative to the master device 14 ₁.

In the present example, the slave devices 14 _(m) are meters used formeasuring an entity, such as electrical power usage. The meters areremote from one another, and are located at various locations formeasuring power at their respective locations. The master device 14 ₁ isa remote terminal unit (RTU) located remote from the meters, which maybe located, for example at a power substation. The greatest distancebetween adjacent devices 14 is limited by the distance that thepropagated signal can travel without attenuating to a level that cannotbe processed. It is known to re-drive (or repeat) optical signals, thusvirtually negating or minimizing any limitations. Advantageously, byproviding communication between devices via fiber optic connectors, thelight signals travel at the speed of light, thus minimizing latencyduring communications, even when signals propagate along relatively longdistances. Furthermore, the fiber optical connectors are not susceptibleto noise, interference, electromagnetic fields, etc., which may exist inthe environs of the devices, particularly in the substation.

The master messages may be, for example, request messages for requestingdata, control signals for controlling operation of the slave device 14_(m), update messages for updating a configuration of the slave device14 _(m), command messages for instructing the slave device 14 _(m) toperform an operation or function, a status update request message forrequesting information regarding the status of the slave device 14 _(m),etc. The reply messages may be for example, data requested by the masterdevice 14 ₁, confirmation of receipt of master message, confirmation ofperformance of update or instructed command, etc.

The master device 14 ₁ may perform processing of the received data,and/or send the data or processed data to another processor, such as ahost processor. For example, the RTU may compile a consolidated reportperiodically (daily, weekly, etc.) of measurement data received from themeters, and send the reports to a processor located at an accountingdepartment associated with the power company for billing customers forpower usage.

The processors 24 and the processor 28 are configured to communicateusing compatible protocols, where the protocol preferably includesembedded addressing and supports half duplex communication. Exemplaryprotocols with embedded addressing used in industrial applications, suchas the power industry, that may be supported by network 10 includeModbus RTU, and Modbus TCP, DNP. The processor 24 and processor 28 eachmay include one or more processing devices, such as a microprocessor, adigital signal processor (DSP), analog devices, logic circuitry, andfurther may include and/or access one or more storage devices, such asROM, SRAM, DRAM, flash memory, etc. The respective processors 24 ofslave devices 14 _(m) and the processor 28 of the master device 14 ₁ mayrespectively execute one or more software modules including a series ofprogrammable instructions which can be stored on a computer-readablestorage medium, such as ROM, flash memory, RAM, a hard drive, CD-ROM,smart card, 3.5″ diskette, etc., or transmitted via propagated signalsfor being executed by the respective processor 24 or 28 for performingthe functions disclosed herein and to achieve a technical effect inaccordance with the invention. The processors 24, 28 are not limited toexecution of the software modules described. The functions of therespective software modules may be combined into one module ordistributed among a different combination of modules.

Processor 24 of each slave device 14(m) executes a software module forprocessing the address associated with each received master message,including determining if the associated destination address (e.g.,destination address embedded within the message) correlates to (e.g.,matches) the address assigned to the processor 24. If the associateddestination address and the assigned address correlate, the non-addressportion of the master message is processed and requested or appropriatetasks are performed, which may include generating and outputting a replymessage. If the associated destination address and the assigned addressdo not correlate, the master message is not addressed to or intended forthe processor 24, and is not further processed by the processor 24. Themaster message propagates with low latency to each processor 24 of theslave devices 14(m) included in the communication ring. Only theprocessor 24 that is addressed processes the non-address portion of themaster message and sends a reply message when appropriate.

Furthermore, the processor 24 may include a delay module, which may be asoftware module included or invoked by the software module executed bythe processor 24, and/or may be a hardware implemented module. Executionand/or processing by the delay module causes a delay for a time periodin proceeding with processing of the master message by the processor 24and/or outputting of the corresponding reply message. The time periodmay be fixed or selectable. The time period may be selected and fixed atinstallation, or may be adjustable after installation, such as by way ofuser request via one or more user input devices on the slave device 14_(m) or a device providing control to the slave device 14 _(m) (such asthe master device 14 ₁), automatic control, and/or software commands.For example, the master device 14 ₁ may send a control master message toa slave device 14 _(m) for adjusting the time period. The time periodmay be selected in accordance with a function of, for exampled, a lengthof the communication ring (e.g., a distance a master message travels(which is the distance around the entire communication ring), a distancethat a master message propagates until reaching the slave device 14_(m), a distance that a reply message travels from the slave device 14_(m) to the master 14 ₁, a distance between the slave device 14 _(m) andan adjacent slave device (14 _(m+1) and/or 14 _(m−1)), and/or the numbern of devices 14 in the communication ring.

The processor 24 receives signals (master messages) propagated alongconnector 20 and transmits signals (reply messages) to be propagatedalong connector 20 via interface 26. Similarly, processor 28 receivessignals (reply messages) propagated along connector 20 and transmitssignals (master messages) to be propagated along connector 20 viainterface 30. The signals propagated along connector 20 are lightsignals, whereas the processors 24 and 28 are configured for receiving,processing and transmitting electrical signals. Accordingly, theinterfaces 26 and 30 include circuitry for communicatingbi-directionally with connector 20, converting between light andelectrical signals and vice versa, processing the electrical signals forforming the signals to be compatible with the corresponding processor 24or processor 28, and communicating bi-directionally with thecorresponding processor 24 or processor 28.

With respect to FIG. 2, the interface 26 associated with a slave device14 _(m) is shown. The interface device 28 includes input channel 16,output channel 18, light to voltage converter (LVC) circuitry 202, andvoltage to light converter (VLC) circuitry 206. At least a portion ofthe interface 26 may be provided on an integrated circuit (IC) chip. Theinput channel 16 receives light signals from connector 20, and directsthe light signals to the LVC circuitry 202. The received light signalsare signals which were output from the output channel 18 of the previousdevice 14 _(m−1) (e.g., a preceding slave or master device). The LVCcircuitry 202 includes circuitry that is known in the art for convertinglight to voltage and outputting an electrical signal having voltagelevels readable by the processor 24 and the VLC circuitry 206 and/orcircuitry associated therewith. The output from the LVC circuitry 202 isdirected along a conductive path 208 which leads to the I/O 32 of theprocessor 24, and more specifically to the input channel 34 of the I/O32.

Preferably, circuitry associated with the VLC circuitry 206 includesgate circuitry 204. The gate circuitry 204 includes circuitry that isknown in the art for receiving first and second signals at first andsecond inputs A and B, respectively, and outputting one signal from anoutput C, where the signal output by the gate circuitry 204 correspondsto first signal when the first signal is received alone, and correspondsto the second signal when the second signal is received alone, withoutcorrupting the first or second signals. Preferably, the gate circuitry204 includes OR gate circuitry as known in the art for performing an ORoperation on the inputs A and B and generating a result at output C. Theoutput C is communicated to the VLC circuitry 206. The first input A ofthe gate circuitry 204 communicates with conductive path 208. The secondinput B of the gate circuitry 204 communicates with path 210, whichcommunicates with the I/O 32 of the processor 24, and more specificallywith the output channel 36 of the I/O 32.

Accordingly, the gate circuitry 204 receives signals transmitted by theprevious device 14 _(m−1) at the first input A, and signals output bythe processor 24 at the second input B. Receipt of signals at input Aand input B is staggered due to the processing time for processing thesignals which were output from the processor 24 and provided to theinput B of gate circuitry 204, whereas the signals at input A were notprocessed by processor 24. The processing time may further include thepredetermined time period associated with the delay caused by the delaymodule. Accordingly, signals at inputs A and B are received one at atime and are provided without being corrupted to the VLC circuitry 206.The VLC circuitry 206 includes circuitry that is known in the art forconverting voltage to light and outputting a light signal thatcorresponds to the received voltage signal. The light signal output bythe VLC circuitry 206 is output from the slave device 14 _(m) via theoutput channel 18, and then via the fiber optic connector 20 to theinput channel 16 of a subsequent (preferably the next) slave device 14_(m+1).

The LVC circuitry 202 and/or the VLC circuitry 206, in addition toconverting energy forms, may function to drive the light signal receivedat input channel 16. The VLC circuitry 206 may be a repeater or adriver, as known in the art. Light signals received at the LVC circuitry202 may have attenuated while propagating from the previous device 14_(m−1) to the slave device 14 _(m). Although attenuated, the LVCcircuitry 202 senses received light signals and converts them to a“high” voltage, where the “high” voltage is a predetermined voltagewhich is readable by the processor 24 and the gate circuitry 204. The“high” voltage does not vary in accordance with strength of the lightsignal. Accordingly, even an attenuated light signal will be processedas a full strength signal, and the attenuation will not affect thestrength of associated signals that will be output from the outputchannel 18 in response to receipt of the light signal.

The degree of attenuation associated with the received light signal maybe a function of conditions such as the distance between the previousstation 14 and the slave station 14 _(m). The strength of the receivedlight signal further is a function of the original strength of thesignal as it was generated by the VLC circuitry 206 of the previousdevice. Furthermore, the sensitivity of the LVC circuitry 202 forsensing light signals determines its ability to recognize attenuatedlight signals. Accordingly, the sensitivity of the LVC circuitry 202 forthe slave device 14 _(m) may be selected in accordance with at least oneof the distance between the slave device 14 _(m) and the previous device14 _(m−1) and the intensity of the light signal upon generation thereofby the VLC circuitry 206 of the previous device 14 _(m−1).

The VLC 206 receives “high” and “low” voltage signals for binary ordigital communication and converts the “high” voltage signals into alight signal, where the light signal has a predetermined intensity. Theintensity of the light signal generated by the VLC circuitry 206 may beselected in accordance with at least one of the distance between theslave device 14 _(m) and the subsequent device 14, and the sensitivityof the LVC circuitry 202 of the subsequent device 14. Due to the abilityto generate or drive the outgoing light signal at a predeterminedintensity, the number of devices included in the network 10 is virtuallyunlimited, provided that light signals propagated between adjacent pairsof devices 14 are readable by the receiving device 14.

Readability of light signals may be insured by adjusting the sensitivityof the LVC circuitry 202, the amplification of light intensity output bythe VLC 206 and/or limiting the allowable distance between adjacentdevices 14. The sensitivity of the LVC circuitry 202 and the intensityof light signals generated by the VLC 206 may be adjustable, where theadjustment may be manual or automatic. Automatic adjustment may be inaccordance with manually input data, sensed data (e.g., signal strengthand/or average signal strength) and/or data received from another device14.

With respect to FIG. 3, the interface 30 associated with the masterdevice 14 ₁ is shown. The interface device 30 includes input channel 16,output channel 18, LVC circuitry 202, and VLC circuitry 206. At least aportion of the interface 30 may be provided on an integrated circuit(IC) chip. The input channel 16 receives light signals from connector20, and directs the light signals to the LVC circuitry 202. The receivedlight signals were output from the output channel 18 of the previousslave device 14 _(n). The LVC circuitry 202 provides the functions andbenefits discussed above with respect to the slave devices 14 _(m). TheLVC circuitry 202 receives the light signals from the input channel 16of the master device 14 ₁ and converts the light signals into voltagesignals which are directed along a conductive path 308 which leads tothe I/O 40 of the processor 28, and more specifically to the inputchannel 42 of the I/O 40.

Data output by the processor 28 via the output channel 44 of the I/O 40,which is in the form of voltage signal, is communicated to the VLCcircuitry 206. The VLC circuitry 206 provides the functions and benefitsdiscussed above with respect to the slave device 14 _(m). The VLCcircuitry 206 outputs a light signal that corresponds to the voltagesignals output by the processor 28 which is output by the master device14 ₁ via the output channel 18, and then via the fiber optic connector20 to the input channel 16 of the subsequent slave device 14 ₁.

In operation, a master message having an associated address thatcorresponds to a slave device 14 _(m) is generated by the master device14 ₁. The master message is output through output channel 18 of themaster device 14 ₁ and propagated along the fiber optic connector 20 tothe subsequent device, which is slave device 14 ₂. The master message isreceived at input channel 16 of slave device 14 ₂ where it is convertedto a voltage signal by LVC circuitry 202 and communicated to the gatecircuitry 204 through which it passes without being altered, and is thenconverted back to a full strength light signal by VLC circuitry 206 andoutput via channel 18 of the slave device 14 ₂ and sent to thesubsequent slave device 14 ₃. The master message thus circulates quicklythrough the communication ring (until it returns to the master device 14₁) without being delayed by processing delays associated with of theprocessors 24 of the slave devices 14 _(m).

In slave device 14 ₂, at substantially the same time that the mastermessage passes through the gate circuitry 204, the master message isprovided to the processor 24 of slave device 14 ₂ via the processor'sI/O 26. If the associated address of the master message does notcorrelate to (e.g., match) the address assigned to the slave device 14₂, the processor 24 does not respond to the master message and does notgenerate any output. If the associated address of the master messagedoes correlate to (e.g., match) the address assigned to the slave device14 ₂, the processor 24 processes at least another portion of themessage, which is a non-address portion of the message.

The slave device 14 ₂ responds to the master message by performing anyinstructions in the message, which may include replying to the mastermessage with a reply message. The reply message may include a datareport. For example, when the slave device 14 ₂ is a power meter, thedata report may include a report of power measured by the meter. Thereply message may include a confirmation that the master message wasreceived and/or results of the requested action (e.g., update softwarein the slave device, change a software parameter, etc.). Furthermore,the processing of the non-address portion of the message may includeprocessing the delay module for creating a delay of a predetermined timeperiod, which may be performed in software and/or hardware.

The reply is output by the processor's I/O 32, passes through the gatecircuitry 204 without being altered, and is then converted back to afull strength light signal by VLC circuitry 206 and output via channel18 of the slave device 14 ₂ and sent to the subsequent slave device 14₃. The reply signal will circulate quickly through the remainder of thecommunication ring, similarly to the circulation of the master message.Slave devices 14 _(m) only process the non-address portion of themessage when the associated address of an address correlates to theirown assigned address. Accordingly, assuming that the destination for thereply message is the master device 14 ₁, no slave devices 14 _(m) willprocess the non-address portion of the reply message.

The processing of the non-address portion of the master message occursas the master message continues to circulate through the remainder ofthe communication ring. The reply message is output from the outputchannel 18 after the master message passes through the output message.The delay between the output of the master message and the reply messagedepends on the degree of processing entailed in processing thenon-address portion of the master message, including the length of thepredetermined time period when the delay module is processed. Even whenthe delay module is not processed the reply message is output fromoutput channel 18 of slave device 14 ₂ after the master message.

If the slave device 14 ₂ was not addressed by the address associatedwith the master message, the master message continues to circulatethrough the communication ring, and the slave device 14 _(m) that has anassigned address that correlates to the address associated with themaster message will process the non-address portion of the mastermessage.

Accordingly, the master message and the reply message are staggered forpreventing data collisions. The master device 14 ₁ operates in a halfduplex mode, and waits for completion of circulation of the mastermessage and/or receipt of the expected replay message and/or a time/outcondition (lapse of a predetermined period of time indicating acommunication failure) before sending another master message. Operationin the half duplex mode minimizes the possibility of a data collision.

It is contemplated that the master device 14 ₁ may send a message whichis destined for more than one slave device 14 _(m). Such a mastermessage may include multiple addresses, no address (indicating that itis for any slave device 14 _(m)), a master address for all of the slavedevices 14 _(m), or a group address for addressing a group of slavedevices 14 _(m). Proper staggering of reply messages sent by the variousslave devices 14 _(m) for avoiding data collisions may be provided bysetting and/or adjusting the time period associated with the delaymodule of the respective slave devices 14 _(m). The master device 14 ₁may knows how many reply messages are expect or the time period withinwhich all reply messages should arrive, and wait accordingly beforesending out a subsequent (or next) master message.

The device 14 may be designed and/or manufactured to process lightsignals which propagate between devices along fiber optic connectors 20.The interface 26 may be integrated with the processor 24, e.g., housedwithin the same housing, and/or the interface 30, similarly, may beintegrated with the processor 28. It is contemplated that the device 14may have originally been designed, manufactured and/or used to processelectrical signals which propagate between devices 14 via electricallyconductive connectors, and that interfaces 26 and 30 are provided formodifying the devices 14 for allowing the devices 14 to process lightsignals propagated between devices along fiber optic connectors 20.

The processor 24 and the interface 26 may have different housings, andlikewise the processor 28 and the interface 30 may have differenthousings. The modified device 14 may include a housing for housing theprocessor 24 and the interface 26 together or for housing the processor28 and the interface 30 together. It is further contemplated that, amodular connection be provided for removably or permanently connectingthe interface 26 to the processor 24 for converting the device 14 into adevice that is capable of processing light signals transmitted betweendevices. Similarly, a modular connection may be provided for removablyconnecting the interface 30 to the processor 28 for converting thedevice 14 ₁ into a master device that is capable of processing lightsignals transmitted between devices.

With respect to FIG. 4, a network 400 is shown in which more than onecommunication ring is provided. As shown, the input channel 16 and/oroutput channel 18 of an electrical device 14 of the network may beconnected to more than one other electrical devices 14. The respectivecommunication rings may use all of the electrical devices 14, or asub-group of the electrical devices 14. The sub-groups may be mutuallyexclusive, or may overlap so that one or more electrical devices 14belong to more than one sub-group. It is further contemplated that thenetwork 400 may include more than one master device; however, it ispreferable that only one device 14 act as a master device at any pointin time.

In the example shown in FIG. 4, devices 14 ₁ and 14 ₅ may operate in amaster mode or a slave mode, with only one of devices 14 ₁ or 14 ₅operating in a master mode at any point in time to avoid datacollisions. Furthermore, communication rings A, B, C and D are shown. Incommunication rings A and B, device 14 ₁ is in master mode and device 14₅ is in slave mode. In communication rings C and D, device 14 ₅ is inmaster mode and device 14 ₁ is in slave mode.

In communication ring A, a master message is transmitted from device 14₁ to device 14 ₂ and the message circulates through the communicationring A (to devices 14 ₃, 14 ₄, 14 ₅, 14 ₆ and 14 ₇) until it returns tothe master device 14 ₁. In communication ring B, a master message istransmitted from device 14 ₁ to device 14 ₄ and the message circulatesthrough the communication ring B (to devices 14 ₅, 14 ₆ and 14 ₇) untilit returns to the master device 14 ₁. In communication ring C, a mastermessage is transmitted from device 14 ₅ to device 14 ₆ and the messagecirculates through the communication ring C (to devices 14 ₇, 14 ₁, 14₂, 14 ₃, 14 ₄,)) until it returns to the master device 14 ₅. Incommunication ring D, a master message is transmitted from device 14 ₅to device 14 ₇ and the message circulates through the communication ringD (to devices 14 ₁, 14 ₂, 14 ₃, 14 ₄,) until it returns to the masterdevice 14 ₅.

As shown, when operating in a master mode, devices 14 ₁ and 14 ₅transmit messages to a device in accordance with the communication ringselected, and when operating in a slave mode transmit messages to asubsequent device in the communication ring being used. Thecommunication ring may be selected by an outside device, such as a hostprocessor in communication with one or more of the master device, or bythe current master device. Instructions to devices 14 ₁ or 14 ₅ tochange mode from slave to master, or vice versa, may be received by anoutside device such as the host processor, or from the acting masterdevice via a master message.

It is further envisioned that a group of at least one electrical device402 and/or a group of devices 404 and 406 be added to the network 400.The communicative connection between output channel 18 of device 14 ₅and the input channel of device 14 ₆ may be disabled, or device 14 ₅ mayoperate in a master mode and select to transmit the message to one ofthe devices 402. Paths F provide for communicatively connecting each ofthe devices 402 to the network 400. The devices 402 may use the samecommunication protocol as devices 14 _(m), or another communicationprotocol, such as by using conventional RS45 hardware and protocols,where an interface (e.g., interface circuitry and/or software) isprovided to interface the devices 402 to the devices 14 _(m). Theinterface may be provided, for example as integrated with one or moredevices 402 and/or device 14 ₅ and/or device 14 ₆.

The devices 404 and 406 are shown in a non-serial configuration. It iscontemplated that sub-groups having other non-serial configurations maybe added and/or included in the network 400 as well. The communicativeconnection between output channel 18 of device 14 ₆ and the inputchannel of device 14 ₇ may be disabled, or device 14 ₆ may be configuredto operate in a master mode and select to transmit the message to one ofthe devices 404 or 406. Paths G are provided for communicativelyconnecting the group of devices 404 and 406 to the network 400. Internalpaths are provided between device 404 and devices 406. Device 404 maycomply with the protocol of the network 400 for receiving a message fromdevice 14 ₆ and providing the message to device 14 ₇, or an interfacemay be provided (e.g., interface circuitry and/or software) to interfacethe devices 404 to the devices 14 _(m). The interface may be provided,for example as integrated with device 404 and/or device 14 ₆ and/ordevice 14 ₇. Accordingly, additional devices 14 _(m) and/or networks ofdevices may be added to the closed communication ring 400.

The described embodiments of the present invention are intended to beillustrative rather than restrictive, and are not intended to representevery embodiment of the present invention. Various modifications andvariations can be made without departing from the spirit or scope of theinvention as set forth in the following claims both literally and inequivalents recognized in law.

1. An electrical metering device for measuring an amount of electricalpower usage of a power distribution system comprising: an input channelfor receiving a master message, the master message being in the form ofa light signal; light to voltage converter (LVC) circuitry for receivingthe master message from the input channel and converting the form ofmaster message into a voltage signal; at least one processor fordetermining electrical power usage data from power measured by theelectrical metering device, the power being supplied remotely from theelectrical metering device, the at least one processor for receiving themaster message from the LVC circuitry, processing the master message andoutputting a reply message in the form of a voltage signal, the replymessage including at least a portion of the electrical power usage data;voltage to light converter (VLC) circuitry for receiving the replymessage from the at least one processor and the master message andconverting the form of the reply message and master message to a lightsignal; and an output channel for outputting the reply message andmaster, wherein the reply message and master message are propagatedalong a fiber-optic connection.
 2. The electrical metering deviceaccording to claim 1, further comprising gate circuitry having a firstinput for receiving the master message and a second input for receivingthe reply message from the at least one processor and circuitry forgenerating an output signal which is provided to the VLC circuitry,wherein the output signal corresponds to a signal received at one of thefirst and second inputs.
 3. The electrical metering device according toclaim 1, wherein the master message has an associated address; and theat least one processor processes content of a non-address portion of thereceived master message depending on if the associated address includedin the master message correlates to an address assigned to the device.4. The electrical metering device according to claim 1, wherein theelectrical metering device is included in a network having a series ofelectrical metering devices, including a plurality of slave devices anda master device.
 5. The electrical metering device according to claim 4,wherein the network operates on an Ethernet medium.
 6. The electricalmetering device according to claim 1, wherein the master message is arequest message for requesting data, control signals for controllingoperation of the device, an update message for updating a configurationof the device, a command message for instructing the device to performan operation or function, or a status update request message forrequesting information regarding the status of the device.
 7. Theelectrical metering device according to claim 1, wherein the replymessage is data requested by the master message, confirmation of receiptof the master message or confirmation of performance of update orinstructed command.
 8. The electrical metering device according to claim1, further comprising a repeater for increasing the signal intensity ofthe master message and reply message output by the output channel. 9.The electrical metering device according to claim 1, wherein the atleast one processor is configured to communicate using at least oneprotocol, wherein the at least one protocol is Modbus TCP.
 10. Theelectrical metering device according to claim 1, wherein the at leastone processor is configured to communicate using at least one protocol,wherein the at least one protocol is DNP.
 11. The electrical meteringdevice according to claim 1, wherein the at least one processor isconfigured to communicate using at least one protocol, wherein the atleast one protocol is Modbus RTU.
 12. An electrical metering assemblyfor measuring an amount of electrical power usage of a powerdistribution system comprising: a single housing; at least one processorcoupled to a power distribution system supplying power remotely from theelectrical metering assembly, the at least one processor configured todetermine electrical power usage data measured by the electricalmetering assembly, the at least one processor being responsive to aninput signal and generating an output signal, the output signalincluding at least a portion of the electrical power usage data, whereinthe at least one processor is configured to communicate using at leastone protocol selected from Modbus TCP, DNP and Modbus RTU; and interfacecircuitry for interfacing between the at least one processor and atleast one input and one output fiber optic connector, wherein the atleast one processor and the interface circuitry are disposed in thesingle housing.
 13. The electrical metering assembly according to claim12, wherein the input signal is a master message.
 14. The electricalmetering assembly according to claim 13, wherein the generated outputsignal is a reply message.
 15. The electrical metering assemblyaccording to claim 12, further comprising a first housing for housingthe at least one processor and a second housing for housing theinterface circuitry, the first housing being external to the secondhousing.
 16. The electrical metering assembly according to claim 12,wherein the interface circuitry includes gate circuitry having a firstinput for receiving the input signal and a second input for receivingthe generated output signal from the at least one processor, the gatecircuitry configured for outputting the received input signal andgenerated output signal.
 17. A network of a plurality of seriallyconnected electrical metering devices, wherein the plurality of seriallyconnected electrical devices form a closed communication ring in whichan output of a respective electrical device of the plurality of seriallyconnected electrical devices is communicatively connected to an input ofa subsequent electrical device of the plurality of serially connectedelectrical devices, the network comprising: at least one master devicecomprising: an input channel for receiving a reply message; at least oneprocessor for generating a master message and processing the replymessage; gate circuitry having a first input for receiving the replymessage, a second input for receiving the master message from the atleast one processor and circuitry for generating repeating the messagesreceived at the first and second inputs; and an output channel foroutputting the master message and reply message, wherein the mastermessage and reply message are propagated along a fiber-optic connection;and at least one slave device comprising: an input channel for receivingthe master message; at least one processor for determining electricalpower usage data from power measured by the at least one slave device,the power being supplied remotely from the at least one slave device,the at least one processor for receiving the master message from theinput channel, processing the master message and outputting the replymessage, the replay message including at least a portion of theelectrical power usage data; gate circuitry having a first input forreceiving the master message, a second input for receiving the replymessage from the at least one processor and circuitry for generatingrepeating the messages received at the first and second inputs; and anoutput channel for outputting the master message and reply message,wherein the master message and reply message are propagated along thefiber-optic connection.
 18. The network according to claim 17, whereinthe network operates using a serial protocol.
 19. The network accordingto claim 18, wherein the protocol is addressable; respective mastermessages generated by the master device are associated with an addressassigned to an individual slave device of the at least one slave device;and the processor of the at least one slave device processes non-addresscontent of the master message depending on if the address associatedwith the master message correlates to the address assigned to the slavedevice.
 20. The network according to claim 17, wherein the at least oneprocessor of the at least one master device is configured for waitingfor response to a master message before sending a subsequent mastermessage.
 21. The network according to claim 17, wherein each pluralityof serially connected electrical metering devices selectably operates ina first mode as the master device or in a second mode as a slave deviceof the at least one slave device.
 22. The network according to claim 17,wherein the network operates on an Ethernet medium.
 23. The networkaccording to claim 17, wherein the at least one processor of the atleast one master device and the at least one processor of the at leastone slave device are configured to communicate using at least oneprotocol, wherein the at least one protocol is Modbus TCP.
 24. Thenetwork according to claim 17, wherein the at least one processor of theat least one master device and the at least one processor of the atleast one slave device are configured to communicate using at least oneprotocol, wherein the at least one protocol is DNP.
 25. The networkaccording to claim 17, wherein the at least one processor of the atleast one master device and the at least one processor of the at leastone slave device are configured to communicate using at least oneprotocol, wherein the at least one protocol is Modbus RTU.
 26. Thenetwork according to claim 17, wherein the at least one master device isa remote terminal unit (RTU).
 27. A method of communicating between anelectrical metering device and other electrical metering devices of aseries of electrical metering devices comprising the steps of: providingat least one electrical metering device of the series of electricalmetering devices configured in a closed communication ring in which anoutput channel of respective electrical metering devices of the seriesof electrical metering devices is communicatively connected by a fiberoptic connector to an input channel of a subsequent electrical meteringdevice of the series of electrical metering devices; measuring by the atleast one electrical metering device electrical power usage data ofpower being supplied remotely from the at least one electrical meteringdevice; transmitting a master message to at least one electricalmetering device along the fiber optic connector; processing the mastermessage by the at least one electrical metering device to generate areply message, the reply message including at least a portion of theelectrical power usage data; and transmitting both the master messageand reply message by the at least one electrical metering device alongthe fiber optic connector.
 28. The method according to claim 27, whereinthe a closed communication ring forms a network, wherein the networkoperates on an Ethernet medium.
 29. The method according to claim 27,wherein the at least one electrical metering devices are configured tocommunicate using at least one protocol, wherein the at least oneprotocol is Modbus TCP.
 30. The method according to claim 27, whereinthe at least one electrical metering devices are configured tocommunicate using at least one protocol, wherein the at least oneprotocol is DNP.
 31. The method according to claim 27, wherein the atleast one electrical metering devices are configured to communicateusing at least one protocol, wherein the at least one protocol is ModbusRTU.